The conversation about illegal immigrants and their impact on our country resurfaced with last week’s shooting of young Cal Poly graduate Katie Steinle.

Katie, 32, had just moved to San Francisco. She was out for an evening walk on the pier when she was shot. Juan Francisco Lopez-Sanchez, 45, has been charged with her murder.

Sanchez is not only an illegal immigrant, but has seven felonies on his criminal record, has served time in federal prison, was on probation in Texas at the time of the murder and had been in custody for an outstanding drug warrant as recently as March, but was released back into the public.

If the story of Sanchez is frustrating, then the resulting death of Katie Steinle is absolutely devastating. It should be the primary goal of every law enforcement agency of the United States to protect its own citizens from foreign intruders who have committed crimes. Perhaps the most frustrating and unfortunate fact is that such crimes are not uncommon.

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Just nine months ago, two Sacramento area sheriff’s deputies were shot and killed by an illegal immigrant. The perpetrator, Luis Enrique Monroy-Bracamonte, was a convicted felon and had been deported twice before fleeing Arizona on drug charges, illegally obtaining a driver’s license in Utah and killing the officers in the Sacramento area. Bracamonte, who had been arrested numerous times before, was not always deported. In 1997 he was held for several months before deportation. After re-entering the country and being arrested again in 1998 for drugs and weapons charges, Bracamonte was not deported at all.

In Orange County, 51 undocumented immigrants with criminal records (more than 1,000 nationwide) were arrested during a series of raids in March of this year. These records included charges of child pornography, vehicular manslaughter, second-degree robbery and DUI, among other things. Not all of these illegal immigrants with criminal records were immediately deported.

When illegal immigrants who have committed a felony crime aren’t deported, they are put into U.S. jails and prisons at the expense of taxpayers. Housing and feeding criminal inmates is expensive. The cost of housing an inmate in the state of California is approximately $47,000 per year.

With California’s prison population sitting just over 130,000, and 10 percent of California inmates with an illegal immigrant status, approximately $611 million of Californians’ hard-earned taxpayer dollars are spent each year incarcerating violent, undocumented offenders.

These criminals often continue to go in and out of our criminal justice, prison and jail systems.

The first half of the solution is to deport undocumented criminals. They should serve out their sentences for their crimes, and then be deported immediately after they are released.

This can’t be the end of the conversations, however.

In the nationwide raid this past March, part of which occurred in Orange County, it was determined that 476 of the 1,000 undocumented criminals had entered the United States more than once. Juan Francisco Lopez-Sanchez, the man charged with Katie Steinle’s murder, had previously been deported five times.

These incidents prove that simply deporting undocumented criminals is not enough.

Criminals like Juan Francisco Lopez-Sanchez seek out cities like San Francisco, self-proclaimed “Sanctuary Cities,” that vow to be lax on enforcing federal deportation policies. These cities are incentivizing undocumented criminals to return to the United States free of punishment.

Their policy stance is inappropriate and is costing American citizens their lives. Our federal, state and local governments should act swiftly to discourage this policy and withhold appropriate funds until cities comply. It is only a matter of time before the policies of “sanctuary cities” offer a bit too much protection to criminals and terrorists and they begin to truly threaten the security of our nation.

I believe the majority of illegal immigrants in America came here in search of work and a better life. Most have no criminal history and want no more than to provide the opportunity to achieve the American dream for themselves and their families. Unless our policies toward those who do come here to commit these crimes, cost our taxpayers money, and harm our citizens become more stringent, there is no hope of our immigration system improving anytime soon.